Before his death, Boris Strugatsky gave a license for writing a sequel to Finnish author Ville Vuorela. Vuorela published The Hollow Pilgrim in 2014 as ebook. Something went wrong with the deal between the small Finnish publisher and Amazon, and now the ebook is annoyingly difficult to find.
https://www.goodreads.com/book/show/23354402-the-hollow-pilg...
Zona by Geoff Dyer is an excellent discourse on the work, which I heartily recommend, and where I first read about this and many other fascinating details.
[1] ...or ker-tan-kep as my own ignorant tongue insists on pronouncing it.
Maybe you mean Roadside Picnic introduced the English word "stalker" to the Russian language? It certainly didn't coin the term (create a new word).
In modern usage it has made its way into books and video games, and people who do tours of Chernobyl have been known to refer to themseves as such.
And I think currently in his steps is following another great Russian director, Andrey Zvyagintsev. The Return was mindblowing.
Stalker consists of 143 shots in just under three hours. A blissful pace.
It was published 7 years before the movie Stalker.
It is a short novel and a great read, it is also a stark contrast to Western SciFi.
https://www.librarything.com/publisherseries/Macmillan%27s+B...
and:
http://www.isfdb.org/cgi-bin/pubseries.cgi?1107
Think Roadside Picnic x 100, because that's the quantity of really excellent science fiction stories and ideas you can expect.
A free (but bad) translation of 'Self Discovery' by Vladimir Savchenko is available if you search. I used this, together with my own physical copy, to make a proper ebook - let me know if you want a copy; I can't locate it at this moment...
And, in my opinion, the finest science fiction short story ever written (apologies to Asimov's Nightfall and Godwin's The Cold Equations): Nine Minutes, by Genrikh Altov https://www.altshuller.ru/world/eng/science-fiction4.asp
That heavily reminds me the "Roadside Picnic" (1972) novel of Strugatsky brothers (that same novel, that coined term "Stalker"). The only difference that the heroes of the novel dealt with consequences of alien civilization visit, and ”Goiânia accident” is purely our's own...